Resuscitation of persons suffering from breathing difficulties is required in a great many different circumstances. It may be required for example, in a hospital or medical operating room. It is frequently required in emergency vehicles such as ambulances, fire appliances, rescue vehicles, life boats and the like. Resuscitation is frequently required in sporting locations, particularly, where water sports are carried on, and in many working environments such as mines, on hydro electrical service vehicles, and in many different military vehicles and installation, which are too numerous to mention.
It is well known that resuscitation may be carried out initially on an emergency basis by mouth to mouth methods. However, it is much more satisfactory to supply fresh air rather than rebreathed air, and better still, to supply air enriched with gas or in certain circumstances, special gas breathing mixtures. In addition, the effort required for mouth to mouth resuscitation is very great, and it can leave an assistant exhausted after only a few minutes.
Consequently, for all these reasons, it is highly desirable to provide some form of simple, manually operated resuscitation equipment, by means of which fresh air, or if available, some form of gas/air or gas mixture, can be supplied to a person suffering from breathing difficulties in an emergency. For reasons of economy, it is necessary that such equipment should be as simple as possible, and preferably manually operated so that it does not require to be connected to a power source.
For this purpose, numerous forms of apparatus have been proposed which are based essentially on a flexible bag or bellows-like device, which may function as an air pump, so that it may be manually squeezed to force air into the lungs of a patient.
Such air bags must however, be capable of being stored in a small space or compartment or in a small emergency pack. They must have a very extended shelf life without any requirement for inspection or testing or servicing, and they must be instantly ready for use as soon as the pack is open. They must operate in a reliable, efficient manner in this way in an emergency which may not occur for years after the equipment has been put in place. Such equipment may be subjected to extremes of weather and temperature, and must be resistent so that it will function even in extremes of heat and cold.
It must also be resistant to moisture which might cause rust in a metal structure, and be resistant to other forms of decay.
One form of air bag has been proposed, in U.S. Pat. No. 3,363,833 which is formed of an integral one piece construction, being molded from a thermoplastic material. The bag described in such patent is of such a type that it can be collapsed for packing, and storage, and is yet ready for use when unpacked. The bag is designed in such a way as to incorporate a wall area around the center of the bag which is of thin-wall construction, so that the user can more readily sense the pressure in the bag. Apparently, it was felt at the time that that product was being developed, that the ability to feel the pressure within the bag was essential to the safe usage of the bag. The theory was that where a person was not in fact breathing at all, or was breathing only with great difficulty, and where the bag was being used to force air into the lungs so as to actually dilate them, that a user of the bag might inadvertently apply excessive pressure to the bag thereby causing damage to the lungs.
There is no doubt that over pressure applied to the lungs especially in the case of small children, can cause damage.
In practice however, it has been found by experience that a bag designed in this way had certain disadvantages which caused even greater problems.
In situations particularly where breathing is arrested or is taking place only with great difficulty, resuscitation is being carried out in haste, and often with feelings of considerable anxiety or even fear, on the part of the assistant or person applying the treatment.
It is well known that unless breathing is restarted within a very short period of time, that irreversible brain damage will take place leading rapidly to death.
Accordingly, the assistant will usually be highly agitated when using the bag, and will be anxiously watching for signs of breathing restarting.
One of the disadvantageous features of the bag described in the above-mentioned patent is that due to its thin-wall construction, it tended to collapse too easily. Once collapsed, the bag then took a considerable length of time to recover to its normal shape. There are no internal springs in such bag for the reasons given above, and it must rely on its own inherent resiliency to recover its original shape. Until it has recovered its own original shape, it is not possible for the operator to compress it again to create a further positive pressure for the patient. During normal non-emergency breathing assistance, the bag will not be compressed more than once for each breath of the patient. Since the normal patient will not inhale more frequently than about thirty to forty inhalations per minute, and provided the recovery time for the bag is no longer than about 1/2 second in length, then there is no problem. However, during emergency resuscitation, when a person is not breathing, the best medical practice recommends that four or five short, sharp pulses of positive pressure should be applied rapidly in quick succession. These initial pulses may be in the order of two or three per second. The slow recovery rate of the bag described in such patent therefore rendered it difficult if not impossible to apply these initial rapid pressure pulses.
In addition to this disadvantage, the slow recovery rate of the bag was, to many operators, an additional cause of stress and worry. The operator, in each cycle, must compress the bag gradually, with a graduated carefully controlled manual pressure and must then release it, waiting for the bag to recover. Under emergency conditions, the slow recovery rate of the bag tended to increase the stress level or worry of the operator so that he would attempt to speed up the resuscitation cycle by either applying the next pressure stroke too soon before the bag had completely filled or, alternatively, applying it too rapidly. This would in turn, produce an excess pressure in the lungs of the user, which was precisely what the design of the bag was intended to prevent.
It has been found by experience that the great majority of operators greatly prefer a bag which has an almost immediate recovery rate. This removes a source of worry or tension, and leaves the operator free to concentrate on the condition of the patient. This in turn, leads to a more carefully controlled and relaxed application of pressure in each cycle, which leads to an improved resuscitation effect, on the patient.
It is therefore, a general objective of the invention to provide a resuscitation bag which is of integral one piece molded construction formed of thermoplastic material, and which is capable of being collapsed and stored for extended periods of time, and which when opened up for use, is provided with a significant degree of inherent resiliency, causing a rapid recovery of the shape of the bag each time it is squeezed.